1. Field of the Invention
The present invention relates to an 8 mm magnetic tape recorder and, more particularly, to circuitry for providing a Video Index Search System (VISS) in an 8 mm format video cassette recorder (VCR) by varying the amplitude of at least one of the frequencies used during recording and playback of an 8 mm magnetic tape. The present invention is equally applicable to camcorders utilizing an 8 mm recording tape format. A method for performing a VISS function is also disclosed.
Korean Patent Application No. 92-13003 is incorporated herein by reference for all purposes.
2. Description of the Prior Art
It is generally well-known that a control track can be formed on a lower end of a tape in order for a head to correctly trace a video track on a magnetic tape recorded by a video cassette recorder using a magnetic tape in the 1/2 inch (12.65 mm) format. In order to precisely control the position of a rotary head with respect to a recorded video signal, a control track has been formed on a lower end of a tape to thereby record a control signal. For 1/2 inch format magnetic tape, the VISS function has been performed by varying the duty cycle of the control signal. However, due to a narrow width of the 8 mm format magnetic tape, the control track cannot be formed on the lower end. Therefore, tracking is performed by utilizing a separate tracking frequency. More precisely, tracking is performed utilizing four tracking frequencies, f1-f4.
It will be appreciated that in order to perform the VISS function, an index signal must be recorded on a predetermined portion of the track domain.
In the prior art system discussed in EP 0 213 731 Al, entitled "Index Signal Detecting System," a description is provided for an index signal detecting system for detecting the index signal recorded on a predetermined track domain during a high speed reproduction mode. According to EP 0 213 731 Al, there is proposed a technique to detect the index signal at all times by way of a rotary head traversely running on the track during the high speed reproduction mode. However, because recording the index signal on a predetermined track domain amounts to, as seen in the foregoing, recording the index signal on a very limited portion of the track domain, it is difficult to detect the index signal during a high-speed search mode or a high-speed reproduction mode.
The present invention was motivated by a desire overcome these problems.